EP2242630A2

EP2242630A2 - Method for the production of extruded profiled elements

Info

Publication number: EP2242630A2
Application number: EP09701971A
Authority: EP
Inventors: Reiner Lay; Paul Wynen
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-01-16
Filing date: 2009-01-13
Publication date: 2010-10-27
Also published as: WO2009090157A3; US20100276845A1; WO2009090157A2; DE102008004636A1; US8728367B2

Abstract

The invention relates to a method for producing extruded profiled elements (3) from an elastomer material. In said method, the extruded profiled element (3) is formed from the elastomer material in a first step, the extruded profiled element (3) is entirely or partly surrounded by a thermoplastic material, the elastomer material that is surrounded by the thermoplastic material is cured, and the thermoplastic material is finally removed again once the elastomer material has been cured.

Description

description

title

Process for producing extruded profiles

State of the art

The invention relates to a method for producing extruded profiles from an elastomeric material.

Extruded profiles of an elastomeric material are used, for example, as a wiper blade for windscreen wipers in motor vehicles. Typically, the squeegee are injection molded or extruded endless. For this purpose, a previously mixed together starting material, for example an unvulcanized natural or synthetic rubber, shaped and vulcanized. Usually double profiles are produced for economic reasons. For the production of individual wiper rubbers, the double profiles are separated after vulcanization and during the optionally subsequent treatment along a cutting edge, which generally represents the subsequent wiping edge.

The production of a wiper blade comprising a squeegee is known, for example, from DE-A 10 2005 000 851. To increase the wear resistance by reducing the coefficient of friction, a coating is applied to the squeegee. As coatings, for example, films or granules are used. The coating can be applied before or after vulcanization.

Also from DE-A 101 25 045 a method for producing a wiper blade is known. The wiper blade has a squeegee with a squeegee lip. To reduce the dry rub, the wiper blade lip is partially made of polyethylene. The polyethylene can either be applied as a coating on the wiper blade or be included in the volume of the wiper blade.

In the wiper rubbers known from the prior art, the coating enters into a non-detachable adhesive bond with the material of the wiper blade rubber. A disadvantage of the known from the prior art method for the production of wiper rubbers is that the not yet vulcanized after shaping profile is permanently deformed by gravity and buoyancy forces in the salt bath used for vulcanization. Currently, squeegee profiles with high wall thicknesses are produced to minimize deformation. However, the high wall thicknesses limit the functional properties of the wiper blade, such as turning noise, in a negative way.

Disclosure of the invention

Advantages of the invention

The process according to the invention for the production of extruded profiles from an elastomeric material comprises the following steps:

(a) forming the extruded profile from the elastomeric material,

(b) completely or partially covering the extruded profile with a thermoplastic material,

(c) vulcanizing the elastomeric material encased in the thermoplastic material,

(d) removing the thermoplastic material after vulcanizing the elastomeric material.

By completely or partially wrapping the extruded profile this can be reinforced. Due to the reinforcement due to the jacket deformation of the extruded profile before and during vulcanization is avoided. In this way, filigree, thin-walled extruded profiles of elastomeric material can be produced without deformation. When the extruded profile is used as a squeegee, lips and scrapers of the squeegee can be made much thinner and with higher process reliability than in the methods known from the prior art.

The extruded profile can be produced, for example, by an injection molding process or an extrusion process. However, the extruded profile is preferably shaped by an extrusion process. In the preferred production of extruded profile by extrusion, the complete or partial encasing of the extruded profile with the thermoplastic material preferably takes place during the extrusion of the extruded profile. As a result of the complete or partial encasing of the extruded profile during the extrusion, the as yet non-dimensionally stable elastomer composition is supported by the thermoplastic material until complete vulcanization. In addition, the elastomeric material is covered by the thermoplastic material, whereby the injection swelling of the elastomeric material is reduced because there is no direct contact of the ambient air with the elastomeric material. This leads to an improvement in the surface quality, whereby the extrusion speed can be increased.

Another advantage is that in a complete sheathing of the extruded profile of the elastomeric material, the surface of the elastomeric material is protected from oxygen during vulcanization. This allows the production of peroxide mixtures also in the hot air process. This is not possible with the methods known from the prior art. According to the prior art, it is necessary to vulcanize peroxide mixtures in a salt bath.

In order to coat the extruded profile during extrusion with the thermoplastic material, a coextrusion process is preferably used to form the extruded profile and to completely or partially encase the extruded profile. In the coextrusion process, the already coated extruded profile exits directly from the tool nozzle.

The thermoplastic material used for the jacket is preferably reused after removal. By reusing the thermoplastic material, only a small amount is required, so that the production costs can be kept low. Another advantage is that the thermoplastic material is not produced as waste in the production of the extruded profile of the elastomeric material.

The elastomeric material for the extruded profile is preferably selected from natural rubber, butadiene rubber, chloroprene Katuschuk, ethylene-propylene rubber, ethylene-propylene-diene rubber, urethane rubber, nitrile rubber, styrene-butadiene rubber, cis -1,4-polyisoprene rubber, silicone rubber, methyl silicone rubber, methyl silicone rubber with fluorine groups or mixtures thereof.

Particularly preferred is the elastomeric material for the extruded profile selected from ethylene-propylene-diene rubber, ethylene-propylene rubber, chloroprene rubber, natural rubber, silicone rubber and mixtures thereof. -A-

In order to easily remove the thermoplastic material from the elastomer material after vulcanization, it is preferred if the thermoplastic material does not form an adhesive bond with the elastomeric material. Thermoplastic polymers are particularly suitable as thermoplastic material. Suitable thermoplastic polymers which do not form an adhesive bond with the elastomeric material are, for example, polyethylene terephthalate (PET), polypropylene (PP), preferably isotactic polypropylene, polycarbonate (PC), polyamide, preferably polyamide 6 (P A6) and high molecular weight polyethylenes (PE-HMW). Thus, the extrudate temperatures, even at high temperature-, preferably remains dimensionally stable in the range from 120 ⁰ C to 200 ⁰ C, the thermoplastic material is preferably used filled. For example, chalk, glass fibers, glass spheres or silicates are used as the filler.

In one embodiment of the invention, the thermoplastic material is extruded with a high wall thickness and a high temperature. The temperature is preferably in the range above 180 ⁰ C, in particular in the range of 180 ⁰ C to 200 ⁰ C. The large wall thickness of the jacket of the thermoplastic material serves as a heat storage, wherein the heat is used to vulcanize the elastomeric material. The temperature of the elastomeric material during sheathing is preferably in the range of 90 ⁰ C to 120 ⁰ C. In this way, it is no longer necessary to perform the vulcanization of the elastomer material in a salt bath or a hot air oven. Thus it can be dispensed with a costly Vulkanisationsstrecke.

In one embodiment, the thermoplastic material used for the cladding is electrically conductive, so that the thermoplastic material can be used as resistance heating for the vulcanization. For this purpose, it is necessary that the electrically conductive thermoplastic material has a sufficiently large resistance to be used as a resistance heater. Such an electrically conductive thermoplastic material usually contains an electrically conductive filler.

Furthermore, it is also possible that at least one friction-reducing substance is added to the thermoplastic material, which migrates to the surface of the extruded profile of the elastomeric material. The addition of the friction-reducing substance reduces the dry-friction value due to the migration to the surface of the extruded profile. As a result, sticking of the extruded profile, when this is used as a squeegee, avoided on the disc of the motor vehicle. In addition, the friction-reducing substance bonds between the thermoplastic material and the elastomeric material reduced, preferably prevented. This also facilitates a subsequent separation of thermoplastic material and elastomer material.

As a friction-reducing substance which may be added to the thermoplastic material, stearic acid amide is suitable, for example. The stearic acid amide does not dissolve in the thermoplastic material and therefore migrates to the surface and interface with the elastomeric material. In general, the stearic acid amide is mixed together with the filler with the thermoplastic material. The proportion of stearic acid amide is preferably in the range of 1 to 5 wt .-%, based on the mass of the thermoplastic material.

The extruded profile produced by the method according to the invention is preferably a profile for a squeegee. Wiper blades can be used for example in windscreen wipers for motor vehicles. Furthermore, wiper rubbers are also used in pullers for window panes.

Further suitable uses for extruded profiles produced according to the invention are, for example, door or window seals. Such door or window seals can be used for example in buildings or preferably in motor vehicles.

If the extruded profile produced according to the invention is a squeegee for a windscreen wiper of a motor vehicle, the extruded profile for the squeegee is preferably designed as a double strip. In such a double strip two wiper blades are connected to each other at their wiper edge. The wiping edge thus acts as a line of symmetry. After completion of the double strip for the production of individual wiper rubbers along the wiping edge, that is the symmetry line is separated. This has the further advantage of producing a sharp edge that results in a better wiping result than a rounder edge, as would arise when a single squeegee is made.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it: 1 shows a section through a double strip for a squeegee with a complete sheath,

2 shows a section through a double strip for a squeegee with support in the middle of the lip,

3 shows a section through a double strip for a squeegee with a thin jacket.

Embodiments of the invention

FIG. 1 shows a section through a double strip for a squeegee with a complete sheathing.

A double strip 1 for a squeegee is an extruded profile 3, in which two wiper rubbers are formed, which are connected to one another at their wiper edge 5. To produce individual wiper rubbers of the double strip 1 is separated at the wiper edge 5. The wiping edge 5 simultaneously represents a symmetry line 7 of the double strip 1.

In order to improve the functional properties of the wiper blade rubber, in particular in order to reduce, for example, transfer noise, it is desirable to form the wiper edge 5 with the smallest possible wall thickness. However, a small wall thickness of the wiping edge 5 leads in known from the prior art manufacturing process that the extruded profile 3 due to gravity and buoyancy forces in the salt bath in which the double strip 3 is vulcanized, permanently deformed. In order to avoid this deformation of the extruded profile 3, the extruded profile 3 is enclosed according to the invention with a jacket 9. In the embodiment shown in FIG. 1, the casing 9 encloses the extruded profile 3 completely.

The extruded profile 3 and the casing 9 can be produced by any manufacturing method known to the person skilled in the art. Usually, the production takes place by an injection molding process or an extrusion process. Particularly preferred for the production of the extruded profile 3, however, is an extrusion process. In order to avoid that the extruded profile is deformed, the casing 9 is preferably formed in a production process with the extruded profile 3. In a preferably used extrusion process, the extruded profile 3 together with the casing 9 is preferably produced by a coextrusion process. Here, the material for the extruded profile 3 and the material for the casing 9 are pressed simultaneously by the tool for forming the extruded profile 3. The extruded profile 3 is thus enclosed during the manufacturing process with the sheath 9. The material for the extruded profile 3 and the casing 9 is generally added via two separate screw machines, which are connected to a common coextrusion tool.

The material for the casing 9 is preferably chosen so that this is dimensionally stable after a very short distance behind the tool and so a deformation of the extruded profile 3 is avoided. As material for the jacket 9, a thermoplastic material is preferably used. Particularly suitable are, for example, polyethylene terephthalate (PET), polypropylene (PP), preferably isotactic polypropylene, polycarbonate (PC), polyamide, preferably polyamide 6 (P A6) and high molecular weight polyethylene (PE-HMW). It is important to ensure that a thermoplastic material is used for the casing, which makes no connection with the material of the extruded profile 3 in order to remove the casing 9 after vulcanization of the extruded profile of the elastomeric material can again.

If the material for the casing 9, for example, friction substances are buried, which are to migrate to the surface of the extruded profile 3, it is preferable to leave the casing even after vulcanization for a predetermined storage time to allow the reibwertmindernden substances on the Surface of the extruded profile 3 to migrate. Migration can be accelerated, for example, by the application of heat, as is the case during vulcanization.

In addition to a complete sheathing 9, it is also possible to coat the extruded profile 3 only partially. This is illustrated by the example of a support 11 in the middle of the double strip 1 in FIG. In this case, the casing takes place only in the region of the smallest wall thickness of the strand profile 3. This occurs exactly at the line of symmetry 7, at which the double strip 1 is separated for the production of the wiper blades. The production of the extruded profile 3 and the support 11 takes place according to the production of the extruded profile 3 with the complete casing 9, as shown in FIG. Also as the material for the support 11, preferably the same thermoplastic materials are used. Advantage of the partial sheathing, as shown in Figure 2, is that only a much lower requirement for thermoplastic material is required to carry out the support 11. However, in the embodiment shown in FIG. However, for example, additives that are to migrate to the entire surface of the squeegee should not be used because too little area of the squeegee is sheathed. However, it is possible, for example, to specifically coat the extruded profile 3 at the positions at which additives are to be applied to the surface. This makes it possible, for example, to achieve a targeted adjustment of the surface properties at certain regions of the extruded profile 3.

In addition to a jacket 9, as shown in Figure 1, which has a comparatively large wall thickness, it is also possible to coat the extruded profile 3 with a thin jacket 13. Even with the thin jacket 13, as shown in FIG. 3, the need for material for the jacket is much lower than in the embodiment shown in FIG. With a sufficiently dimensionally stable material for the sheathing of the thin sheath 13 is sufficient to prevent deformation of the extruded profile 3 in the further production. Also, a thin jacket 13 is already sufficient, for example, to prevent oxygen from reaching the surface of the extruded profile 3. In addition, it is avoided by a complete sheathing of the extruded profile 3 that this can swell, since the material of the casing 9, 13 is dimensionally stable and thus the material of the extruded profile 3 is prevented from expanding. This leads to a better surface quality of the elastomer material of the extruded profile 3. In addition, the better dimensional stability can also increase the extrusion speed and thus also the production speed.

By a complete sheathing, as shown in Figures 1 and 3, the surface of the elastomeric material is protected from substances from the environment. In particular, no oxygen can reach the surface of the elastomeric material. This makes it possible to produce peroxide mixtures in the hot air process, which is not possible with the methods known from the prior art.

In all three illustrated embodiments, the vulcanization of the elastomer material of the extruded profile 3 takes place after the jacket. The vulcanization takes place by any method known to the person skilled in the art. Usually, the vulcanization is carried out in the salt bath or in the hot air or infrared channel.

After vulcanization and optionally storage to allow additives to migrate to the surface of the elastomeric material of the extruded profile 3, the sheath 9, the support 11 and the thin sheath 13 is removed again. The removal takes place, for example, by peeling or stripping off the casing 9, the support 11 or the thin shell 13. For ease of peeling or stripping, for example, notches 15 are provided in the shell 9.

After removal, the thermoplastic material from which the sheath 9, the support 11 and the thin sheath 13 are formed can be remelted and reused.

In addition to the vulcanization in salt bath or hot air or infrared channel, it is also possible, for example, the thermoplastic material of the sheath or the thin shell 13 to add an electrically conductive additive, so that the thermoplastic material is made electrically conductive. With sufficient resistance, the material of the sheath 9 or of the thin sheath 13 can then be used as a resistance heating source for the vulcanization.

In order to be able to remove the thermoplastic material of the casing 9, of the support 11 or of the thin casing 13 from the elastomer material of the extruded profile 3, a thermoplastic material is preferably used which does not form an adhesive bond with the elastomer material of the extruded profile.

In addition to the production of double strips 1 for wiping rubbers, as shown by way of example in FIGS. 1 to 3, the method according to the invention can also be used to produce any other extruded profile made of an elastomeric material. It is thus possible, for example, to produce extruded profiles for sealing rubbers or very thin-walled tubes by the method according to the invention.

Claims

claims

1. A process for producing extruded profiles (3) from an elastomeric material, comprising the following steps:

(e) forming the extruded profile (3) from the elastomeric material,

(f) completely or partially sheathing the extruded profile (3) with a thermoplastic material,

(g) vulcanizing the elastomeric material encased in the thermoplastic material,

(h) removing the thermoplastic material after vulcanizing the elastomeric material.

2. The method according to claim 1, characterized in that the extruded profile (3) is formed by an extrusion process.

3. The method according to claim 2, characterized in that the complete or partial sheathing of the extruded profile (3) with the thermoplastic material during the extrusion of the extruded profile (3).

4. The method according to claim 3, characterized in that for forming the extruded profile (3) and for complete or partial sheathing of the extruded profile (3)

Coextrusion is used.

5. The method according to any one of claims 1 to 4, characterized in that the thermoplastic material of the sheath (9, 11, 13) is used again after removal.

6. The method according to any one of claims 1 to 5, characterized in that the E-lastomermaterial for the extruded profile (3) is selected from natural rubber, butadiene rubber, chloroprene rubber, ethylene-propylene rubber, ethylene-propylene-diene Rubber, urethane rubber, nitrile rubber, styrene-butadiene rubber,

Cis-1,4-polyisoprene rubber, silicone rubber, methyl-silicone rubber with fluorine groups or mixtures thereof.

7. The method according to any one of claims 1 to 6, characterized in that the thermoplastic material does not form an adhesive bond with the elastomeric material.

8. The method according to any one of claims 1 to 7, characterized in that the thermoplastic material is selected from polyethylene terephthalate, polypropylene, polycarbonate, polyamide, preferably polyamide 6, and high molecular weight polyethylene.

9. The method according to any one of claims 1 to 8, characterized in that the thermoplastic material is electrically conductive, so that the thermoplastic material can be used as resistance heating for vulcanization.

10. The method according to claim 9, characterized in that the thermoplastic material contains at least one electrically conductive filler.

11. The method according to any one of claims 1 to 8, characterized in that the elastomeric material is vulcanized by the heat of the jacket of the thermoplastic material.

12. The method according to any one of claims 1 to 11, characterized in that the thermoplastic material at least one friction-reducing substance is added, which migrates to the surface of the extruded profile (3) of the elastomeric material.

13. The method according to any one of claims 1 to 12, characterized in that the extruded profile (3) is a profile for a squeegee.

14. The method according to claim 13, characterized in that the extruded profile (3) for the squeegee is designed as a double strip (1).